Gradual weightloss no better than crash diets in the long term

New study shows that people who lose weight slowly and steadily are no more likely to keep it off in the long term than those who opt for crash dieting - but some experts say doctors should be able to recommend crash diets because even short-term weight loss will improve the health of the obese

The old assumption that people who go for slow and steady dieting keep the weight off in the long term, while crash dieters pile it back on, is wrong, according to a new study. But unfortunately there is no reason for crash dieters to get very excited - in the long term, both gain back most of the weight they lost.

This was a trial in Australia which recruited 200 obese adults who were randomly assigned to a slow and steady diet or a crash diet. The slow and steady group reduced their calorie intake by around 500 calories a day for 36 weeks.

The crash dieters, on the other hand, ate a very low calorie diet of between 450 and 800 calories a day for just 12 weeks - unsuitable for some people and needing a doctor’s approval. Those of either group who lost 12.5% of their bodyweight were then put on a maintenance regime for three years to try to keep them at their new weight.

The researchers from the University of Melbourne found that those who lost weight faster were more likely to reach the target weight. That is not a big surprise, because a dieter’s morale goes up as the pounds fall off. The crash dieters also ate meal replacements, which meant they did not have to count the calories themselves or think about what to cook each night.

But the dispiriting and yet predictable finding of the study was that it did not matter in the long term which diet people had adopted. After three years, 71% - nearly three-quarters of those who took part - had regained their original weight.

However, experts pointed out that it can be important for obese people to get their weight down rapidly even just in the short term. Prof Nick Finer, consultant endocrinologist and bariatric physician at University College London Hospitals, said the NHS should act on the findings:

If we couple these findings to those from other groups that have shown dramatic and immediate improvements in diabetes and blood pressure with rapid weight loss, the use of low energy meal replacements should be part of NHS approaches to treatment.